the 3g eclipse downpipe are compatible with the 8g galant. but note that there are different versions of the downpipe for both the 8g and 3g eclipse, so the one you get might or might not fit.
although i haven't seen any aftermarket downpipe sold for the 3g or the 8g. usually they are bundled with the aftermarket headers. but some member might have one laying around.
if all else fails, find a good exhaust shop to make you one.
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